Glueless interlock for double walled folding boxes



Jam 2, 1951 R. B. MELLER 2,536,334

GLUELESS INTERLOCK FOR DOUBLE WALLED FOLDING BOXES Filed April 17, 19483 Sheets-Sheet l INVENTOR- W QMM ATTORNEY Jan. 2, 1951 R. B. MELLER2,536,384

GLUELESS INTERLOCK FOR DOUBLE WALLED FOLDING BOXES Filed April 17, 1948KSheets-Sheet 2 INVENTOR.

M MMAM t; ATTORNIYS W T a RY R B MELLER 2 GLUELESS INTERLOCK FOR DOUBLEWALLED FOLDING BOXES 3 Sheets-Sheet 3 Fig. 8

' A; ATTORNEYi w F m n 1 d '6 mm JF Patented Jan. 2, 1 951 GLUELESSm'rnnnocx ron noma- WALLED rommo noxss Reginald B. Meller, Oakland,Calif., assignor to Demise-Jason Company, San Francisco, Calif., acorporation of California Application April 17, 1948, Serial No. 21,688

21.Claims. (Cl. 229-35) This invention relates to improvements incartons, boxes, trays, and other structures made from blanks ofcardboard, paperboard, or other suitable foldable sheet material,hereinafter collectively referred to as boxes or folding boxes.

The invention is particularly directed to folding boxes which, eitherpartially or entirely, are composed of walls of multiple thickness.

The invention provides a novel interlock for connecting together,without the use of adhesives, staples, or other special securing means,walls of a box in rigid corner forming re ationship where all of thewalls, or at least part of them, are of multi-ply thickness. Theinvention thus extends to boxes requiring heavier than single thicknesswalls for strength, a form of interlock which, in a somewhat sim lermodification, has found wide adoption throughout the industry for thesetting up of boxes having single thickness walls.

According to the invention, two multi-ply walls, or a single ply and amulti-ply wall, meeting at a corner are mechanically interlocked by apeculiar inter-engagement of cut edges formed on or in the stock. Theresulting box corner has the strength and rigidity of a glued or stapledconstruction. The'novel interlock is permanent and cannot, except by theuse of special tools, be separated or disengaged and is secure againstaccidental disengagement by forces acting on the box from the inside orthe outside.

The present invention ofiers the advantage of H eliminating gluingorstapling operations in the 1' setting up of a hollow box fro'ma fiatblank, lead-v ing to production rates far in excess of those at- Itainable for glued boxes. The invention further leads to simplificationof the mechanical equipment for setting up the boxes .and reduces itscost. Moreover, the invention permits economical setting up of doublewalled boxes of certain relatively small sizes which heretofore couldnot be following description taken in connection with the accompanyingdrawings forming a part of it in which Figure 1 is a plan viewof a flatbox blank embodying the invention, the inside surface of the blankfacing the observer;

Figure 2 is a fragmentary plan view of a corner portion of the blankshown in Figure 1, in which certain dash dotted lines indicate therelative position which certain elements assume after forming of theblank into hollow box form;

Figure 3 is a plan view of the comer portion of the blank shown inFigure 2 after a gluing and foding operation for forming walls of doublethickness;

Figure 4 is a sectional side view of an end wall, a section being takenon line 4-4 of Figure 3:

Figure 5 illustrates an alternative form of construction of the end wallin a view corresponding to that of Figure 4;

Figure 6 is a perspective view of a box set up from the blank shown inFigures 1, 2 and 3;

Figure 7 is a fragmentary plan view of a comer portion of a modifiedblank, the inside surface of the blank facing the observer;

Figure 8 is a fragmentary plan view of a corner portion of a form ofblank for making shallow boxes; and

Figure 9 is a perspective view of a comer portion of a box set up fromthe blank of Figure 8.

Inthe following description and in the claims, various structuraldetails will be identified by specific names for convenience. The names,

however, are intended to be as generic: in their application'as the artwill permit. Corresponding reference characters refer to correspondingparts in the several figures of the drawings.

In the drawingsaccompanying, and forming part'of this specification,certain speciflc'disproduced economically by gluing because ofdisproportionately high cost due to intricacy of the gluing machines andthe relatively low produc-'- tion rates of such machines.

These and various other features, objects and advantages of theinvention will appear more fully from a consideration of the detaileddescription which follows accompanied by drawings showing, for thepurpose of illustration, preferred embodiments and applications of theinvention.

The invention also consists in certain new and improved details ofconstruction as hereinafter set forth and claimed.

Although the characteristic features of the invention which are believedto be novel will be particularly pointed out in the claims appendedhereto, the invention itself, its objects and advantages, and the mannerin which it may be carried out may be better understood by referring tothe closure of the invention is made for the purpose Qt -explanationofbroader aspects of .the invention, but it is understood. that thedetails may be modified in various respects without departure from theprinciples of the invention and that the invention may be applied toother structures than the ones shown. I

The blank A shown in Figure 1 issubdivided by several scored'fold linesto provide a bottom panel H to which outer side wall panels i2 and i3are hinged along side fold lines it and i5. Inner side wall panels l6and ii are hingedly connected to the outer side wall panels along foldlines l8 and I9, respectively.

Outer end panels 20 and 2i are hingedly connected to the bottom panel Halong end fold lines 22 and 23, respectively, and inner end panels 24and 25, slightly narrower than the outer end panels, are hingedlyconnected to the outer end panels 20 and 2| along fold lines 2. and 21,respectively. Additional folding scores 28, 23, 36 and 3| extend acrossthe-inner end panels 24 and 25 adjacent the fold lines 26 and 21. Thepurpose of these additional folding scores will become apparenthereinafter.

Flaps 32 and 33 are hingedly connected to the outer end panel 20 alongfold lines 34 and 35, respectively. These fold lines are either alignedwith, or parallel and slightly offset with respect to, the side foldlines l4 and if to compensate for wall thickness in the succeedingfolding op-' erations, asis customary in the art. Flaps 36 and 31 arehingedly connected to the outer end panel 2| along fold lines 38 and 33in a similar mann r as described in connection with the flaps 32 and 33.

Internal cuts 40, 4|, 42 and 43 separate the outer side wall panels l2and I3 into portions which may be resiliently flexed with respect toeach other for the purpose of opening the cuts and inserting portions ofthe flaps 32, 33. 36 and 31 into them. The internal cuts 40, 4| 42 and43 are preferably of bent outline to form internal tongues 44, 45, 46and 41 in the panels l2 and I3.

Cut edges are formed on the flaps 32, 33, 36 and 31 by external cuts 48,49, 56 and extending into the body of the flaps from outer edges. Theorientation and shape of the cuts 48, 49, 59 and 5| is such thatportions of the cut edges formed by the cuts in the flaps 32, 33, 35 and31 upon assembly of the blank into box form move into substantialcoincidence with portions of the internal cuts 40, 4|, 42 and 43 so thatan edgeto-edge engagement results between. cut edges of the flaps andcut edges of the outer side wall panels, as will hereinafter beapparent.

External tongues 52, 53, 54 and 55 are formed by the external cuts 48,49, 56 and 5|, respectively. These external tongues are resilientlydefiectable with respect to the remainder of the flaps 32, 33. 36 and 31in the same manner as the internal tongues 44, 45, 46 and 41 may beflexed with regard to the remainder of the outer side wall panels I: andI3.

The external tongues 53, 54 and 55 include tab portions 56, 51, 56 and59 extending partially beyond the confines of the external tongues 44,45, 46 and 41 as is particularly apparent from Figure 2 in which theflap 32 is shown in dashdouble-dot-lines superimposed upon the panel |2in the position which the flap assumes in the set up box. The purpose ofthese tab portions will become apparent from a consideration of theassembly procedure of the blank which will be described hereinafter.

Internal cuts 66, 6|, 62 and 63 are formed in the inner side wall panelsl6 and I1. These internal cuts are preferably of reversely curvedoutline and form oppositely directed tongues 64, 65, 66, 61, 68, 69, and1| in the irmer end wall panels l6 and I1, respectively. The tonguesformed by the internal cuts 60, 6|, 62 and 63 are so located and shapedas to make more effective and secure the interlock formed between cutedges of the external cuts 48, 49, 50 and 5| and edges formed by theinternal cuts 40, 4|, 42 and 4 Referring specifically to Figure 2, inwhich the elements are shown on an enlarged scale, it will be seen thatthe tongue 64 overlaps the external tongue 52 in the position in whichthe blank is folded into hollow box form. The overlap causes the flap 64'to deflect the external tongue 52 with respect to the remainder of theflap 32 into edgeto-edge engaging position with the internal cut 43 aswill also become apparent from an inspec- 4 tion of Figure 6 hereinafterdescribed in greater detail.

The oppositely pointed tongue 65 overlies the tab portion 56 of theexternal tongue 62. This tab portion, as will later become apparent,secures the interlock against accidental disengagement. The tongue 65which bears down upon the tab portion 56 maintains the tab portion inlooking position and protects it against contact with the box contents.

The internal cuts 6|, 62, and 63 and the tongue.- formed thereby areidentical in outline and function with the internal cut 60 justdescribed. A detailed description of the tongues 66, 61, 63, 69, 10 and1| may therefore be dispensed with.

The assembly of the blank A into hollow box form may proceed as follows:

Adhesive a is first applied to marginal portions of the inner side wallpanels l6 and I1 and to marginal portions of the inner end wall panels24 and 26 as indicated in Figure l. The panels are then folded aboutfold lines I8, i9 and 26, 21, respectively, to bring the inner side wallpanels and the inner end wall panels face-to-face with the outer sidewall panels and the outer end wall panels, respectively, and pressure isapplied to the glued portions to produce a secure bond. During thefolding the inner end wall panels 24 and 25 are preferably slightlyflexed at the fold lines 28 and 29 to form ridges near the upper edge ofthe end walls as is apparent from Figure 4.

The resulting blank A, of which a corner portion is shown in Figure 3,has double thickness side walls |2, |6 and double thickness end walls2|), 24. The blanks A are flat except for the slight ridge at the foldlines 28 and 30. They may be shipped and stored in fiat collapsedcondition and are available for immediate setting up into hollow boxform at the plant of the user of the boxes.

The setting up of the blanks A into hollow box form may be carried outon manually operated machinery of simple construction, where relativelysmall volumes are involved, or may be set up on automatic high speedmachinery where the volume demand is large.

The setting up of the blank A into hollow box form and the interlockingof the blank at the comers involves the following operations:

The side panels |2, |6 and |3, H are first folded along the side foldlines l4 and I5 to bring the side walls into substantially u rightposition with respect to the bottom panel H. In this position the stockof the side walls is flexed at the internal cuts in order to open thecuts in the outer wall panels. This may be accomplished by pressing withsuitable finger shaped tools against the inner side wall panels asindicated in Figure 6 where a finger 12 is shown as flexing the internaltongue 68 outwardly. Flexing of the internal tongue 68 causes flexing ofthe internal tongue 46 in the outer side wall panel which overlies it.During the flexing of t e internal tongues the rema nder of the sidewall is supported, preferably adjacent the tongues to be flexed so thatapertures are formed in the side wall into which the corresponding flaps32, 33, 36 and 31 may be inserted.

The four internal tongues in the side walls are preferably flexedsimultaneously so that all four cuts 40, 4|, 42 and 43 are onened forinsertion of portions of the thus 32, 33, 36 and 31 therein The endwalls 26. 24 and 2|, 25 are then folded with respect to the bottom panelabout the tion of the end walls is then continued while simultaneouslythe portions 52, 53, 54 and 55 of the fla s are guided into the openedslits 40,41, 42 and-43. I

This operation brings the edgesof the external tongues 52,53, 54 .and,55 into substantial coincidence, with portions of the internal cuts 40,4|, 42 and 43 as is quite apparent from Figure 2 where the-coincidenceof the cut edge 48 with a portion 407 of the cut 40 is shown Theposition of.the finger shaped tools with respect to the variousportions. of the blank during the locking operation is apparentfrorn,Figure 6 where it is seen that th finger shaped tool 12 bears againsttheside wall It, I 2 with its outer surface-13, opening the cut in theside wall, while permitting the external tongue-14 in the respectiveflap to move underneath its inner surface 14. After insertion of theflap portions 52, 53, 54 and 55 underneath the respective finger shapedtools, the tools are drawn or moved towards the inside of the box untilthe tab portions 58, 51, 58 and 5,9, which previously-lay on the outsideof the outer side wall panels are drawn to the inside of the outer sidewall: panels. i I

In this position. the edges of. the. external tongues 52. 53,..54and55which were in coincidence with edge portionsflof the internal cut 40.41, 42, and 43 move into edge-toqedge engagement therewith and aremaintained in this position by the tab portions on the respectiveexternal tongueswhich now lie on between the outer and the innersidewall panels l2, l and. l3, 11, respectively. Y l

The setup box A" is then removed from the folding mechanism. As shown inFigure 6 the finger shaped tools which opened the cuts in the side wallsand which pulled the tab portions from the outside of the outer wallpanels to the inside can easily disengage. themselves from the box bymovement in the direction of the arrow 75, it being understood that thearrow is used to indicate relative motion since it may be preferred toremove the folded box from its forming mechanism rather, than move the]forming mechanism away from the set upbox. It may therefore be preferredto move the finished box A? in a downward direction in which event,however, the finger 12 moves along the dash dotlines 16. In either casethe finger shaped tool is free to disengage itself from the blank byreason of the peculiar shape of the internal cut in the inner sidewallpanel which permits the finger to move freely out of the cut 62atBZ'.

After the box is disengaged from its forming and locking mechanism, theinternal tongues 65. S1, 69 and libearagainst'the respective lock tabswhichlie betweenthese tongues and the outer sidewall panels and securelyhold these look tabs in place and protect .them from contact with thebox contents. v

The set up box is very strong and rigid and its walls resist forcesacting on the walls from the outside and from the inside.

Theside edges of the inner end wall panels 24 and 25 bear. against theside wallpanels l3 and It in edge-to-surface relationship and prevent 6folding of the side walls towards the inside of the box. The side wallsare protected against out ward folding by the flaps 32, 33, 36 and I!overlyingthe side walls.

The end wall panels 20 and bear against the side edgesof the side wallsand prevent inward folding of the end panels. Outfolding of the endpanels is prevented by the edge-to-edge en age ment between the externaltongues 52, 53, 54 and 55 and the internal cuts 40, 4|, 42 and 41. Thisedge-to-edge interlock is very strong and resists a con iderable amountof'force which maybe exerted against the end panels from the inside ofthe box. Such force subjects the board to compression at the edge-to-ede engagement and constitutes the most favorable form of load for paerboard and box board since board ollers relatively great resi tance tocompression as compared to tear-resistance which is com aratively low.The compression force exerted against the bo rd at the points ofedge-fo-edge' cont ct lies in the plane of the board and the boardoffers its greatest resistance tndeformation if s bjected to force nthis dire tion. external ton ues 52. 53. 54 and 55 throu h the two pliesof the side walls furthermore locks the two plies toget er and impartsaddit onal rigidity to the s de walls a ainst bul in out if. for examle, force i exerted aeainst'the upper edges of the side walls at foldlines [8 and I9;

Instead of form ng a r d e in t e surface of the inner end panels as sown in Figure 4. the end panels may be folded along a sin le' fold line15' as s own in Fi ure 5 to provide suificient abutment al ng ts s de eges for theside walls ii. i i and l3. H. A re ativ lv w de score may beimpressed into the board at 25' to prevent the board from iorrrdne ashar crease so t at the nner end'nanel forms'an inward bulge 24'. asshown in Figure 5. Y The blank B of which a corner portion is shown inFigure com ris s a bottom anel 16 to which side walls and end walls arehineedly connected along fold lines I1 and 18. Theside wall comprises anouter side wall panel I! and an inn'r side wall anel h nged to the outerpanel along a fold'line BI. The end wall comprises an outer end panel 82and an inner end panel 83 hinged to the outer end panel along a foldline 84. A flap 85 is hingedlv' connected to the outer end anel 82 alonga fold line 86. An external out 81 extends nto the fla 85 and forms an.external ton ue 88 there n having a tab portion 89. The outer edge ofthe fiapincludes a portion 90 whosepurpose will presently becomeapparent.

An internal cut 9| forms an internal tongue 92 in the outer sidewallpanel 89. This internal cut comprises a portion 93 adapted to-enter intoedge-to-edge engagement with a cut edge formed by the external, cut 81.It further includes a portion 94 forming an edge past'which a tabportion 89 is forced-in assembling the blank into corner formingposition. Lastly, theinternal cut comprises a portion 95 adapted toengage the edge portion 90 of the flap 85 tov provide anedge-to-edgeinterlock effective in a direction opposite with respect to theinterlock double interlock efiective in two opposite directions and isnot dependent on an engagement between the side edge of the side wallsand the surface of the outer end wall panel for preven- The thr ading ofthe tion of the end walls from folding towards the inside of the box.

The advantage of the interlock shown in Figure 7 is its freedom fromplay or lost motion. The abutting or interlocking edges may be cut withgreat accuracy and close tolerances are easier to maintain in cuttinginterlocking edges than in providing equally close tolerances for thesurface-to-edge abutment between the outer end panel and the edge of theside wall.

An internal cut 96 of reverse curvature is formed in the inner sidepanel it. It forms two internal tongue 81 and st in the panel, thetongue 91 serving to flex the external tongue it into edge-to-edgeengagement and the tongue it saving to bear down upon, and protect, thetab portion 88 as hereinbefore described in connection with blank A.

The assembly of the blank B into box form proceeds in the same manner ashereinbefore described in connection with the blank A and the resultantbox differs from the box A" of Figure 6 only in that two pairs of edgesat each cornerv flap provide an interlock effective in two oppositedirections whereby the resulting interlock is completely free from playor lost motion.

The blank C shown in Figure 8 corresponds in most particulars to theblank shown in Figure '1 and primed reference numerals are employed todesignate corresponding parts. A detailed description of the blank maytherefore be dispensed because of the similarity.

The blank C is particularly designed for shallow boxes. Its interlockcorresponds to that of theblank B except for the absence of a cut edgecorresponding to edge til on the flap. Correspondinsly. no edge portioncorresponding to cut edge 95 is present. The only point of differencebetween the blanks B and C, except the absence of edges 90 and 95 is thelocation ot'the' internal cut 95' which extends to the fold line ll Thisarrangement permits reduction of the height of a side wall and permitsvery shallow double walled boxes to be formed economically whichheretofore were not economical to make by gluing.

A corner portion of a box set up from the blank ls shown in Figure 9.

The invention thus provides an improved construction for boxes havingdouble side and end walls permitting assembly of the blanks into hollowbox forms on relatively simple machinery at high production rates. Theboxes embodying the invention are comparable in strength to glued boxes,but are generally superior to glued boxes from a point of economy sincecomplicated box forming and gluing machine may be dispensed with. In itsplace a relatively simple forming mechanism is used which may beoperated at high or slow speeds depending on production requirements.This folding and locking mechanism costs only a fraction of the cost ofan ordinary forming and gluing machine and has the added advantage ofbeing operable at the wide range of speeds since no critical gluesetting time need be observed.

Boxes embodying the present invention are not only extremely strong butalso are relatively tight permitting relatively finely divided materialto be packaged. This advantage is attained by providing the cuts in theside wall panels in offset relationship. Comparable tightness is notnormally found in gluelessly assembled boxes.

Obviously the present invention is not restricted to the particularembodiments herein shown and described, but may be applied with equalbenefit to other forms of boxes. Numerous additions, omissions andsubstitutions may be made in adapting the invention to specific needswithout departure from the spirit and essence of the present invention.

What is claimed is:

1. In a box blank of foldable sheet material including a main panel; afirst side wall hingediy connected to the main panel along a first foldline. said first side wall being composed of an outer panel and an innerpanel foldable into overlapping face-to-face relationship with the outerpanel; a second side wall hingedly eonneeted to the main panel along asecond fold line extending at an angle with respect to said first i'oldline; and a fiap hingedly connected to said second side wall along athird fold line extending at an angle with respect to said second .foldline, said flap being foldable into face-tofaee overlapping positionwith respect to the first side wall, the improvement permittingformation. without the use of adhesives. of said panel, walls, and flapinto a rigid box corner, the improvement comprising, an internal cut insaid outer panel severing the stock of said outer panel to form twopanelportions defiectable with respect to each-other for opening said out; anexternal cut edge on said flap forming an edge of a defiectable externaltongue of said fiapysaid internal cut and said external cut edge beingso located with respect to each other that portions of said out and saidcutedge are in substantial coincidence when said first and second sidewall are in corner forming position permitting an edge portion of thecut edge to engage an edge portion formed by said internal cut when saidexternal tongue is inserted into said opened cut: and an internal cut ofbent outline in said inner panel forming an internal tongue in saidinner panel adapted to engage the outside surface of said externaltongue, thereby maintaining said external tongue in flexed position inwhich the external tongue engages an edge of the internal cut in theouter panel.

2. A folding box set up from a blank as defined in claim 1.

3. The box blank structure as set forth in claim 1 in which, inaddition, the second side wall is composed of an outer panel and aninner panel, the inner panel being foldable against the inside surfaceof the outer panel in overlapping face-to-face relationship, the innerpanel being narrower than the outer panel and furnishing with its sideedges an abutment against which the first side wall panel rests when thetwo side walls are in corner forming position. the abutment preventingfolding of the first side wall towards the inside of the corner.

4. A folding box set up from a blank as defined in claim 3.

5. In a box blank of foldable sheet material including a main panel; afirst side wall hingedly connected to the main panel-along a first foldline. said first side wall being composed of an outer panel and an innerpanel foldable into overlapping face-to-face relationship with the outerpanel; a second side wall hingediy connected to the main panel along asecond fold line extending at an angle with respect to said first foldline; and a flap hingedly connected to said second. side wall along athird fold line extending at an angle with respect to said second foldline..said fiap being foldable into face-to-face overlapping positionwith respect to the first side wall, the improvement permittingformation, without the use of adhesives, of said panel, walls, and flapinto a. rigid box corner, the improvement comprising, an internal cut ofbent outline in said outer panel forming an internal tonguev in saidouter panel adapted to be resiliently flexed with respect to theremainder of said outer panel foropening said internal cut; an externalcut edge on said flap forming an edge of a defiectable external tongueof said flap, said internal cut.

and said external cut edge being so located with respect to each otherth'atportions of said cut and saidcut edge are in substantialcoincidence when said first and second side wall are in corner, formingposition permitting an edge portion of the cut edge to engage an edgeportion formed by said internal cut whensaid external tongue is insertedinto said opened cut; and an internal cut of bent outline in said innerpanel forming an internal tongue in said inner-panel adapted to engagethe outside surface of said external tongue, thereby maintaining saidexternal tongue in flexed position in which the external tongue engagesan edge of the internal cut in the outer panel. H r ,7

6. A folding box set up from a blank as defined in claim 5.

, 7. The box blank structure as set forth in claim inwhich, in addition,the second side wall is composed of an outerpanel and an inner panel,thev inner panel being foldable against the inside surface of the outerpanel 1H1 overlappingface-,to-face relationship, the inner, panel beingnarrower than the outer panel and furnishing with its side edges anabutment against which the first side wall panel rests when the two sidewalls are in corner forming position, the abutment preventing folding ofthe, first side wall towards the inside of the comer.

8. A folding box set up from a blank as'deflned' in claim 7.

9. In abox blank of foldable sheet material including a main panel; afirst side wall hingediy,

connected to tne niain panel along a first ioid line, said first s dewail being composed of an outer panei and an inner panel foldable intooverlapping face-to-face relationship with the outer panel; a second,side wall hlngedly; connected to the main panel along a second i'oldline, extending at an angle with respect to sa.d first iold line; and anap hingedly connected to said second side wall along a thlld iold lineextending at an angle with respect to said second fold line, said napbe-ng foldable into lace-toface overlapping position with respect to thefirst side wall, the improvement permitting Iormation,

without the use or adhesives, of said panel, walls,

and nap into a rigid box corner, the improvement comprising, an internalcut of bent outline in said outer panel forming an internal tongue insaid outer panel adapted to-be resiliently flexed with respect to theremainder of said outer panel for opernng; said internal cut to permitinsertion of saldflap therein in assembling'the blank; an external cutedge on said fiap forming an edge of a deflectable external tongue ofsaid flap, said internal cut and said external cut edge being so locatedwith respect to eachother that portions of said out and sad cut edge arein substantial coincidence when said first and second side wall are incorner forming position permitting an edge portion of the cut edge toengage an edge port;on formed by said internal cut when said externaltongue is inserted into said opened cut; and an internal cut of bentoutline in said inner panel forming an internaltongue in said innerpanel underlying, whensald inner panel is folded against said outerpanel, the internal tongue in said outer panel rearwardly of theinternal tonguein said outer panel with respect to the adjacent sideedge of the inner panel, the internal tongue in said inner panel beingadapted to engage the outside surface 01' said external tongue, therebymaintaining said external tongue in, flexed position in which theexternal tongue engages an edge of the internal cut in the outer panel.

10. A, fold ng boxset up from =aiblank as definedin claim, 9. '1, ll.The box blank structure as set forth in claim -9 in which, in' addition,the second side wall is composed of an outer paneland an inner panel,the inner'panel being foldable against the inside surface of the outerpanel in overlap ping face-to -face relationship, the inner panel beingnarrower than the outer panel and fur nishing with its s deedges anabutment against which the first sidewall panel rests whenthe' two sidewalls are in. corner forming position, the abutment preventing, foldingof the first side wall towards the inside of the corner.. 12. A foldingbox set up from a blank as definedin claim 11. i i l 13. In a box blankof foldable sheet material including a main panel; a first sidewallhingedly connected-to the main panelalongafirst fold line, saidfirst side wall being composed of an outer panel and an inner .panelfoldable into overlapping face-to-face relationship with the outerpanel; a second side wall hingedly connected to the main panel along asecond foldline extending at an angle with respect to said.

first fold line; and a flap hingedly connected to said second sde wallalong a third foldline extending at an angle with respect to said secondfold line, said flap being foldable into face-toface overlappingposition with respect to the first side wall, the improvement permittingformation, without the use of adhesives, of said panel, walls, and flapinto a rigid box corner, the im-' edge of a deflectable external tongueof said flap, portions of said internal cut and said external out edgebeing in substantial coincidence when said first and second side wallare in corner forming position permitting anedge portion of the cut edgeto engage an edge portion formed by said internal cut when saidexternal'tongue is'inserted intosaid opened cut, the external tonguebeing of such outline relatively to'the outline of said external tonguethat a tabportionof said external tongue extends beyond the confines ofsaid internal tongue if the first side wall,

the second side wall and the flap are'in corner forming position inwhich they are to be .inter-' locked; and an internal cut of reverselybent outline in said inner panel forming two oppo-" sitely directedinternal tongues insaid inner panel, one of said last named tonguesbeing' adapted to engage the outside surface of said external tongue,thereby maintaining said external tongue 'in flexed position in whichthe 5 external tongue engages an edge of the internal cut in the outerpanel, the other of the last 11 namedtonguesbeingadaptedtobearagainstsaid tab portion to urge said tab portion against the inner surface ofthe outer panel after assembly of the corner which assembly includesforcing said tab portion from a position overlying the outside surfaceof the outer panel to a position overlying the inner surface of theouter panel.

14. A. folding box set up from a blank as defined in claim 13.

15. The box blank structure as set forth in claim 13 in which, inaddition, the second side walliscomposedofanouterpanelandaninner panel,the inner panel being foldable against the inside surface of the outerpanel in overlapping face-to-face relationship, the inner panel beingnarrower than the outer panel and furnishing with its side edges an.abutment against which the first side wall panel rests when the two sidewalls are in corner forming position, the abuts ment preventing foldingof the first side wall towards the inside of the corner.

18. A folding box set up from a blank as defined in claim 15.

17. In a box blank of foldable sheet material,

including a main panel; a first side wall hingedly connected to the mainpanel along a first fold line, said first side wall being compoud of anouter panel and an inner panel foldable into overlapping iace-to-facerelationship with the outer panel; a second side wall hingedly connectedto the main panel along a second foid line extending at an angle withrespect to said first fold line; and a flap hingedly connected to saidsecond side wall along a third fold line extending at an angle withrespect to said second fold line, said flap being foldable intoface-to-face overlapping position with respect to the first side wall,the improvement permitting formation, without the use of adhesives, ofsaid panel, walls, and flap into a rigid box corner, the improvementcomprising, an internal cut of bent outline in said outer panel formingan internal tongue in'said outer panel adapted to be resiliently flexedwith respect to the remainder of said outer panel for opening saidinternal cut; an external cut edge on said fiap forming -an edge of adefiectable external tongue of said fiap, said internal out and saidexternal cut edge being so located with respect to each other thatportions of said out and said out edge are in substantial coincidencewhen saidfirst and second side wall are in corner forming positionpermitting, when said external tongue is inserted into said opened cut,an edge portion of said out edge to engage an edge portion formed bysaid internal cut thereby pre-@ 55 venting movement of said tongue inthe direction of withdrawal from said opened cut, the external tonguebeing further so shaped to engage with another edge portion a furtheredge Portion formed by said internal cut, thereby preventing movement ofsaid tongue in the opposite direction, the external tongue including atab portion extending beyond the confines of said internal tongue ifthefirst side wall, the second side wall and the flap are incorner'forming position in which they are to be interlocked; and aninternal cut of reversel'y bent outline in said inner panel forming twooppositely directed internal tongues in said inner panel, one of saidlast named tongues being adapted to engage the outside surface of saidexternal tongue, thereby maintaining said external tongue in fiexedposition in which the external tongue engages an. edge of the internalcut in the outer panel, the other of the last named tongues beingadapted to bear against said tab portion to urge said tab P rtionagainst the inner surface of the outer panel after assembly of thecorner which assembly includes forcing said tap portion from a positionoverlying the inner s rface of the outer panel.

18. A folding bo fined in claim 17.

19. The box blank structure as set forth in claim 17 in which, inaddition, the second side wall is composed of an outer panel mid aninner panel, the inner panel being foldable against the inside surfaceof the outer panel in overlapping face-to-face relationship. the innerpanel being narrower than the outer panel and furnishing with its sideedges an abutment against which the first side wall panel rests when thetwo side walls are in corner forming position, the abutment preventingfolding of the first side wall towards the inside of the corner.

20. A folding box set up from a blank as d in claim 19.

21. In a folding box made from a blank of foldable sheet material andincluding. a main panel; side walls hingedly connected to the main panelalong side fold lines, each of the side walls being composed of an outerpanel and an inner panel lying face-to-face with the outer panel; endwalls hingedly connected to the main panel along end fold linesextending transversely with respect to the side fold lines; and fiapshingedly connected to the end walls and folded into faceto-faceoverlapping position with respect to the side walls, the improved cornerconstruction comprising, for each corner, an internal cut in said outerpanel severing the stock of said outer panel to form two panel portionsdefiectable with respect to each other for opening said out; an externalcut edge on the respective fiap forming an edge of a defiectableexternal tongue on said fiap, said internal cut and-said external outbeing in substantial coincidence permitting an edge portion of said outedge to engage an edge portion formed by said internal cut when saidexternal tongue is inserted into said out; an internal cut of bentoutline in said inner panel forming an internal tongue in said innerpanel adapted to engage the outside surface of said external tongue,thereby maintaining said external tongue in fiexed position in which theexternal tongue engages an edge of the internal cut in the outer panel;and means associated with said side walls and end walls for locking saidside walls against folding from their upright position towards theinside of the box.

REGINALD B. HELLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 483,502 Schmidt Sept. 27, 1892637,838 Vernon Nov. 28, 1899 1,468,696 Bray Sept. 25,1923

2,228,377 Wendt, Jr. Jan. 14, 1941 2,316,362 Poe Apr. 13, 1943 2,366,419Meller Jan. 2, 1945 2,450,035 De Mian Sept. 28, 1948 FOREIGN PATENTSNumber Country Date 398,044 Great Britain Sept. 7, 1933 447,136 GreatBritain May 13. 1936 set up from a blank as de-

